Subject:
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Re: Pneumatic "One Leg at a Time" Robot Circuit
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Newsgroups:
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lugnet.technic
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Date:
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Tue, 13 Sep 2005 23:15:19 GMT
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Viewed:
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3655 times
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In lugnet.technic, Mark Bellis wrote:
> In lugnet.technic, Kevin L. Clague wrote:
> > In lugnet.technic, Mark Bellis wrote:
> > > A while ago I saw an electric robot on TV that had 6 legs in 2 rows of 3 and
> > > moved one leg at a time forwards (lift, forward, down), then all back together.
> > >
> > > I thought this is an ideal application for Lego pneumatics.
>
> (SNIP)
> > >
> > > http://www.brickshelf.com/gallery/mbellis/Technic/Pneumatics/Building-Blocks/pneumatic_one_leg_at_a_time_robot_circuit.jpg
> > >
> > > There are 5n+3 steps in the cycle, where n is the number of legs. The circuit
> > > uses 3n+1 (or 4n+1) cylinders and 7n+2 valve switches.
> > >
> > > Load bearing is accommodated by the fact that all the legs share the weight, so
> > > if a small pressure drop occurs when a raised foot is lowered, all the other
> > > feet would rise a bit rather than one leg rising all the way, and it would equal
> > > out by the time the raised foot was fully lowered.
> > >
> > > As well as walking robots, this circuit lends itself to any function that
> > > requires several sub-systems to operate in sequence, with a global reset at the
> > > end.
> > >
> > > Mark
> >
> > Hi Mark,
> >
> > Now I know what to build next..... a four legged walker that lifts one leg at
> > a time. On paper it looks like I can get one made for 1+2n pistons and 2+4n
> > switches. This assumes that legs mechanically lock when weight bearing. I don't
> > use pneumatic differential pair logic when making walkers. I stick with single
> > switch AND gates that Mark Terrabain turned me on to.
> >
> > In general I don't think that differential pair logic is the most cost
> > effective way to build sequencers because they are so much more expensive to
> > implement.
> >
> > Kev
>
> This one has moved away from my usual differential logic. Each leg module has a
> flip-flop for the foot and hip, which does 3 out of 4 movements and waits for
> the fourth to be done all legs together.
>
> I see how single switch AND gates work for several legs in parallel, but this
> robot is one leg at a time, which has a greater overhead of pneumatic parts.
> Perhaps using 3 leg modules with a few single switch AND gates would make a
> decent 6-legged 2 at a time robot. It doesn't have the same steering capability
> that you've added with reversers though, but it was directly modelled on the
> robot I saw, rather than the ideal function.
I understand that leg 0 is moved up forward then down, leg 1 is moved
up/forward/down, leg2 is moved up/forward/down, leg 3 is moved up/forward/down,
and finally leg 0, leg 1, leg 2 and leg3 are moved back.
I don't quite understand why you think the above design is not amenable to using
single switch AND gates.
I've done a paper design, but the proof is in the pudding, so I'll make that
uses the single switch AND gates.
I just happen to have four legs that just waiting for a reason to walk.
>
> I had a surprise the other day. Looking on my old computer I discovered that
> I'd drawn a 1+4 AND gate for myself long before I joined the online community!
> I wouldn't quibble about credits, though it just shows how great minds think
> alike! The discovery was not a surprise in one sense, because I wondered how I
> had developed my octopus arm without first making an AND gate. The octopus arm
> is an old design too, but it combines single and differential logic. I think I
> drew a first circuit sketch and then minimised it, probably removing a third of
> the switches!
Quibbling about credit wouldn't do any good, because my invention was
independent from yours. I've never had access to your computer so clealy mine
was independent ;^) It is interesting that it took you so long to recognize my
1+4 as a valid AND gate (even though you already invented it and forgot)
>
> Mark
Kev
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Message has 1 Reply:
Message is in Reply To:
 | | Re: Pneumatic "One Leg at a Time" Robot Circuit
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| (...) (SNIP) (...) This one has moved away from my usual differential logic. Each leg module has a flip-flop for the foot and hip, which does 3 out of 4 movements and waits for the fourth to be done all legs together. I see how single switch AND (...) (19 years ago, 13-Sep-05, to lugnet.technic)
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